A comparator compares voltage levels of two input signals and outputs a comparison result. A flash-type A/D converter includes several comparators. A 4-bit flash-type A/D converter includes at least 15 comparators. To convert a high frequency analog signal into a digital signal, a flash-type A/D converter that includes comparators performing high speed operation is desired.
The relevant technique is disclosed in Japanese Laid-open Patent Publication No. 2010-109937, Japanese Laid-open Patent Publication No. 2010-223553, Japanese Laid-open Patent Publication No. 10-065542, Japanese Laid-open Patent Publication No. 2000-307391, Japanese Laid-open Patent Publication No. 2006-270726, Japanese Laid-open Patent Publication No. 2001-223754, Japanese Laid-open Patent Publication No. 2003-273938, or D. Schinkel, E. Mensink, E. Klumperink, E. Van Tuiji, B. Nauta: “A Double-Tail Latch-Type Voltage Sense Amplifier with 18 ps Setup+Hold Time”, IEEE, ISSCC 2007, Dig. Of Tech. Paper, pp. 314-315, February 2007.